1. Field of the Invention
The present invention relates to a position-detecting system and a reference points detecting system therefor to be used in a moving vehicle, and more particularly to a position-detecting system and a reference points detecting system for use in a moving vehicle such as a moving automobile, an unmanned mobile and carrying device in a factory, or an automated vehicle for use in agriculture, civil engineering machinery and the like.
2. Description of the Prior Art
Heretofore, as a system for detecting a current position of a moving body such as the moving vehicles as described above, there has been proposed a system provided with a means for scanning a light beam emitted from a moving body in the circumferential direction or every azimuthal direction centering around the moving body, light-reflecting means for reflecting to return the light beam in the direction of incident light and secured at at least three positions apart from the moving body, and a beam receiver means for receiving light reflected from the light-reflecting means (Japanese Patent Laid-open No. 67476/1984).
In the above mentioned prior art, differential azimuths between adjoining two of three light-reflecting means centering around the moving body are detected on the basis of received beam output of the light-receiving means, and then a position of the moving body is operated based on the detected differential azimuths and positional information of the light-reflecting means which have been previously set.
In the above described system, however, there has been such a case where light beam emitted from a beam source mounted on the moving vehicle could not be directed to the light-reflecting means positioned at reference points because of an inclination or vibration of the moving vehicle, or a case where the light-receiving means on the moving vehicle receives light reflected from the objects other than the expected light-reflecting means those described above.
When real reflected light is not positively received by a light-receiving means, the position of the moving vehicle is erroneously calculated so that the moving vehicle cannot be traveled along a prescribed course.
As means for solving the above described problem, te present inventors proposed the following technique in U. S. Pat. Ser. No. 67/420063 filed on Oct. 11, 1989. Means is provided which receives the light reflected by light-reflecting means disposed at the reference points and detects the azimuth of the light-reflecting means based on the receiving interval of the reflected lights, and based on the azimuth of the light-reflecting means detected by the detecting means in the previous scanning cycles, the azimuth of the light-reflecting means to be detected in the next scanning is predicted.
If no light-reflecting means is detected in the above described predictive direction in the next scanning, it is deemed that the light-receiving means to be detected has been missed, the direction of the missing light-reflecting means is estimated, and the position and advance direction of the moving vehicle are calculated on the basis of the estimated azimuth.
In the above patent specification, however, the predicted azimuth of the light-reflecting means to be detected in the next scanning is set as a predictive azimuth having a particular width or allowance angle. And te allowance angle is set at a constant value regardless of the distance from the moving vehicle to the reference point. Therefore, if the distance between the reference point and the moving vehicle is long, the considerable portion in front of and behind the scanning direction constitutes a range which is contained within the allowance angle.
Accordingly, if the reflected light from any other wrong reflecting object existing within the allowance angle and near the expected light-reflecting means is received before the light reflected by the expected light-reflecting means, the reflected light from the wrong reflecting object may be determined to be the true reflected light from the expected light-reflecting means disposed at a reference point.
When the reflected light from the light-reflecting means is not detected, the azimuth of the light-reflecting means which is not detected this time is estimated according to the azimuth of the light-reflecting means which was detected before, so if such estimation process is repeated, the difference between the actual value and the estimated value may accumulatively increase.